[Intel-gfx] Performance regression using Firefox between 2.14 and 2.15

[Clemens Eisserer]

Hi,

For quite some time now I experience slow scrolling on some pages when
using FireFox,
now I took the time to find the culprit.
The slow scrolling only manifests when maximizing FireFox' window
(screen size is 1920x1280),
and manifests in "after-scrolling" (scrolling although mouse already stopped).
During scrolling, X doesn't respond to new input.

It seems with 2.15 there is a performance regression, causing some
pages to scroll slow.
On my system the following page scrolls slow:
http://news.orf.at/stories/2081416/2081417/,
especially if the small images on the top need to be repainted.
Also

During slow scrolling, intel_gpu_top reports a completly busy ring (0%
idle), ring space at ~10%
and the following load:
Color clalculator: 99%
Bypass FIFO: 99%
Map filter: 97%
Intermediate Z: 62%
Windowizer: 55%
Pixel Shader: 1%
Setup engine: 1%

My System is:
- Fedora Core 15 (updated)
- intel 2.15 & 2.16 (both show the slowdown, 2.14 was ok)
- Intel 945GM
- Core2Duo T7200 (2x2ghz, 4mb shared L2 cache)

I pasted my Xorg.log to: http://pastebin.com/74NXbrTp

Is there anything further I should try to track this problem down?

Thank you in advance, Clemens